Articles
WATER QUALITY FOR HYDROPONICS: NUTRIENTS, BACTERIA AND ALGAE IN RAINWATER PONDS
Article number
644_71
Pages
533 – 539
Language
English
Abstract
For hydroponic cultivation water with good quality is needed.
Compared to determinations in hydrology, for use in hydroponics the term water quality can be limited to the presence of specific ions, phytotoxic substances or organisms, and substances or organisms clogging the irrigation systems.
To test the statement that rainwater matches these demands the quality of two rainwater ponds was investigated.
Total ion concentration did not differ between the ponds although concentration of ions, such as NH4+, Zn2+ and Fe2+, did.
Electrical conductivity amounted to an average of 4 mS m-1. Concentrations of unwanted ions, such as Na+, Cl– and SO42-, and others, such as H2PO4–, Fe2+ and Zn2+, were low and did not contribute much to the total ionic strength.
NO3–, NH4+ and Mg2+ were determined to have values lower than 80 µmol L-1 and therefore present no problem in preparing nutrient solution.
Relative high amounts of K+ with more than 200 µmol L-1 and Ca2+ with more than 840 µmol l-1 contributed mostly to the total ion concentration.
The relatively high concentrations of Mg2+ (max. 70 µmol L 1) and Ca2+ are responsible for a high amount of HCO3– and thus a pH always above 6 and up to 9.5. Population density of heterotrophic, culturable bacteria did not differ significantly between the ponds but depended on the test media used.
The mean values at log 3.8 on Tryptic Soya Agar and at log 4.9 CFU ml-1 on Kings medium are higher than respective results from the literature.
The general development and composition of the algal community was very similar in the two ponds examined as well as in the sample collected near the surface and the bottom of the ponds.
Unicellular green algae dominated, among them Scenedemus spp.
Other species found were determined and listed.
Overall, the cell density showed wide fluctuations, especially in summer.
Connected with low temperature conditions, it is suggested that algae are not the main cause of filter clogging observed under arid conditions.
The quality of the rainwater investigated was assessed to be well suited for the use in hydroponics without any problems in nutrient concentration, bacterial and algal development.
Compared to determinations in hydrology, for use in hydroponics the term water quality can be limited to the presence of specific ions, phytotoxic substances or organisms, and substances or organisms clogging the irrigation systems.
To test the statement that rainwater matches these demands the quality of two rainwater ponds was investigated.
Total ion concentration did not differ between the ponds although concentration of ions, such as NH4+, Zn2+ and Fe2+, did.
Electrical conductivity amounted to an average of 4 mS m-1. Concentrations of unwanted ions, such as Na+, Cl– and SO42-, and others, such as H2PO4–, Fe2+ and Zn2+, were low and did not contribute much to the total ionic strength.
NO3–, NH4+ and Mg2+ were determined to have values lower than 80 µmol L-1 and therefore present no problem in preparing nutrient solution.
Relative high amounts of K+ with more than 200 µmol L-1 and Ca2+ with more than 840 µmol l-1 contributed mostly to the total ion concentration.
The relatively high concentrations of Mg2+ (max. 70 µmol L 1) and Ca2+ are responsible for a high amount of HCO3– and thus a pH always above 6 and up to 9.5. Population density of heterotrophic, culturable bacteria did not differ significantly between the ponds but depended on the test media used.
The mean values at log 3.8 on Tryptic Soya Agar and at log 4.9 CFU ml-1 on Kings medium are higher than respective results from the literature.
The general development and composition of the algal community was very similar in the two ponds examined as well as in the sample collected near the surface and the bottom of the ponds.
Unicellular green algae dominated, among them Scenedemus spp.
Other species found were determined and listed.
Overall, the cell density showed wide fluctuations, especially in summer.
Connected with low temperature conditions, it is suggested that algae are not the main cause of filter clogging observed under arid conditions.
The quality of the rainwater investigated was assessed to be well suited for the use in hydroponics without any problems in nutrient concentration, bacterial and algal development.
Authors
D. Schwarz, R. Grosch, W. Gross
Keywords
algal communities, heterotrophic bacteria, ion concentration, nutrient concentration, rainwater quality, temperature
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